|
Thorn XE/D 2kW Lamp for Centurion Tank 98-1520 |
Mercury lamps had also been investigated for such applications, but their long-run up time posed problems for military service. British Siemens conceived a rather intriguing design that was used for a short while though - a compact source mercury arc tube concealed within a magnetically-operated shutter all in a large outer bulb. The lamp was kept simmering at a low current, and when full light output was required the current was increased, the response in luminous flux being immediate and the increased arc current resulting in a magnetic field which opened the shutter.
The xenon lamp pictured here had to be specially modified for use on the 24V DC battery circuit employed in the Centurion tank. The third auxiliary electrode was connected to a small Tesla transformer, which allowed the arc to be instantly ignited while only the standard low operating voltage was applied across the main electrodes. In common with AEI and Thorn's other Xenon lamps, the end seals are of a very intricate design employing multiple annular molybdenum foils.
| Manufacturer: | Thorn Lighting Ltd | |
| Lamp Power: | 2000 Watts | |
| Lamp Current: | 85 Amps | |
| Lamp Voltage: | 23.5 Volts | |
| Cap Type: | Special with cone centres | Flexible Leads |
| Bulb Type: | BTT-65 | |
| Bulb Finish: | Clear | Open Quartz |
| Electrodes: | Solid Tungsten (thoriated) | Zr getter on anode |
| Arc Length: | 6.0-7.0mm | |
| Atmosphere: | Xenon | |
| Luminous Flux: | 80,000 lm (@ 100 hrs) | |
| Luminous Efficacy: | 40.0 lm/W (@ 100 hrs) | |
| Colour Temperature & CRI: | 5600K | Ra |
| Chromaticity Co-ordinates: | CCx: | CCy: |
| Rated Lifetime: | 2000 hours | |
| Warm-up & Re-strike Time: | Instant | Instant |
| Burning Position: | Vertical or Horizontal ± 15° | |
| Overall Length: | 315 ± 5 mm | |
| Light Centre Length: | 152.5 ± 2 mm from single electrode end | |
| Factory: | Leicester | England |
| Date of Manufacture: | Approx. 1970 | |
| Original Value: | GB £151.80 | (1972) |
